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N.Korea prisoner's death a metaphor: Kirby

A seemingly harmless, cheeky gesture while touring North Korea saw Otto Warmbier become "a dispensable pawn in a great international chess game", former High Court judge Michael Kirby says.

Mr Kirby says the young university student's life, horrific treatment and death serves as a metaphor for nameless statistics behind North Korea's demilitarised zone.

The 22-year-old died on Monday, less thank a week after being returned home to the United States from North Korea, where he had been imprisoned for stealing a propaganda banner.

"His plight should draw our attention to the sufferings of an entire people subjected in North Korea to daily acts of fearsome disproportion and violence," Mr Kirby said in a speech at the Sydney Institute on Wednesday evening.

Mr Warmbier fell into a coma shortly after being sentenced to 15 years jail in early 2016.

He died six days after being transported back to the US with doctors saying he suffered extensive loss of brain tissue.

Mr Kirby, who chaired a 2013 United Nations commission of inquiry on human rights violations in North Korea, described the communist country as a "pitiless place".

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"Nothing in my previous 35 years as a judge in Australia had prepared me for the systematic, widespread and gross human rights violations that were disclosed in the evidence about the conditions in that country," he said.

He said the punishment Mr Warmbier received for his foolish behaviour was totally disproportionate and his jailers "brutal, secretive and neglectful".

"His plight should draw our attention to the sufferings of an entire people subjected in North Korea to daily acts of fearsome disproportion and violence," he said.

"In 1945, the world promised that never again would it turn away from crimes against humanity.

"That promise has not yet been delivered."

Mr Kirby said the young man's death tells the world it should act, but questioned if it would.

"That is the puzzle left to humanity by the life and death of Otto Warmbier."